Using ecphoric confidence ratings to discriminate seen from unseen faces: the effects of retention interval and distinctiveness.

Theories of confidence processing for recognition judgments suggest that confidence indexes the degree of match between a presented stimulus and an image in memory (ecphoric similarity). Recent research has demonstrated that having participants rate their confidence that a face had been previously seen provides an equivalent or a better index of the stimulus's status than does eliciting a simple binary response (Sauer, Brewer, & Weber, Journal of Experimental Psychology: General 137: 528-547, 2008). Using a face recognition paradigm, we manipulated retention interval and stimulus distinctiveness to directly test the suggestion that confidence indexes ecphoric similarity and to probe the boundary conditions for using confidence ratings to discriminate seen from unseen faces. Consistent with the proposed ecphoric basis for confidence ratings, mean confidence was higher for previously seen than for unseen faces, and conditions conducive to the formation of strong memories improved confidence-based discrimination. In all conditions, after the application of a classification algorithm, confidence ratings provided a more sensitive index of face status (i.e., seen or unseen) than did binary responses.